Not with a AAA game like GTA V, he will need to lower the settings quite a bit for the GTX 1050 to perform decent.
Or not.
http://www.guru3d.com/articles-pages/amd-radeon-r9-rx-480-8gb-review,18.html
59FPS at 1440. Not bad. The chart says max detail, so either live with the 59FPS avg, or dial a few things back to hit a solid 60FPS. What about Dota 2?
http://www.userbenchmark.com/PCGame/FPS-Estimates-DOTA-2/3684/146623.0.0.1440p.0
First site I found with a way to look at Dota 2 with a RX480. ~120FPS. Looks like he'll be fine there. Before "someone" jumps on me for not knowing what I'm talking about or that I'm implying any game will run, step off. While not the greatest card ever, the 480 should run most games at 1440 with ok to good settings with 60+ frame rates. There will be some where it chokes, and there might even be a couple where it falls flat on it's face. But if it's what the OP has, after looking at the games mentioned, it's fine at 1440.
OP, you said you worried about your CPU. Increasing res does put a mild load on the CPU, but we are talking very small. At least once you get to 1080 and above. At this point the load increases SO MUCH on the GPU that you notice that WAY before you see the hit on the CPU. I agree with the above posters, the 480 will give out before the CPU does. If you want to buy a new 1440 monitor, do so. (It's 1080 or 4k for me, no interpolation for me.) You'll need a GPU upgrade before a CPU upgrade so keep that in mind.